Structural and electrochemical characteristics of Li4−xAlxTi5O12 as anode material for lithium-ion batteries

Al-doped Li4Ti5O12 in the form of Li4−xAlxTi5O12 (x = 0, 0.05, 0.1 and 0.2) was synthesized via solid state reaction in an Ar-flowing atmosphere. Al-doping does not change the phase composition and particle morphology, but easily results in the lattice distortion and thus the poor crystallinity of Li4Ti5O12. Al-doping decreases the specific capacity of Li4Ti5O12, while improves remarkably its cycling stability at high charge/discharge rate. The substitution of Al for Li site can enhance the electronic conductivity of Li4Ti5O12 via the generation of mixing Ti4+/Ti3+, whereas impede the Li-ion diffusion in the lattice. Excessive Al causes large electrode polarization due to the lower Li-ion conductivity, and thus leads to low specific capacity at high current densities. Li3.9Al0.1Ti5O12 exhibits a relatively high specific capacity and an excellent cycling stability.